The phrase "brings on board" typically indicates the act of recruiting or including someone in a team or project. Antonyms for this phrase would therefore imply the opposite action, such as excluding or dismissing someone. Some antonyms could include "leaves out," "cuts loose," "eliminates," or "rejects." Alternatively, antonyms could focus on the absence of recruitment or inclusion, with phrases like "ignores," "avoids," or "disregards." Whatever the antonym, the implication is that someone is not joining a team or project, either because they were never considered or because they were actively excluded from participation.